Using array map to filter results with if conditional

Question

I am trying to use an array map to filter a object a bit further to prepare it to send to the server to for saving. I can filter to 1 key value, which is great, but I want t

Answer 1

You should use Array.prototype.reduce to do this. I did do a little JS perf test to verify that this is more performant than doing a .filter + .map.

$scope.appIds = $scope.applicationsHere.reduce(function(ids, obj){
    if(obj.selected === true){
        ids.push(obj.id);
    }
    return ids;
}, []);

Just for the sake of clarity, here's the sample .reduce I used in the JSPerf test:

  var things = [
    {id: 1, selected: true},
    {id: 2, selected: true},
    {id: 3, selected: true},
    {id: 4, selected: true},
    {id: 5, selected: false},
    {id: 6, selected: true},
    {id: 7, selected: false},
    {id: 8, selected: true},
    {id: 9, selected: false},
    {id: 10, selected: true},
  ];
  
  	
var ids = things.reduce((ids, thing) => {
  if (thing.selected) {
    ids.push(thing.id);
  }
  return ids;
}, []);

console.log(ids)

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EDIT 1

Note, As of 2/2018 Reduce + Push is fastest in Chrome and Edge, but slower than Filter + Map in Firefox